Particle migration of suspensions in a pressure-driven flow over and through a porous structure

TL;DR

This study uses MRI to analyze how non-Brownian suspensions with varying particle concentrations migrate and alter flow profiles when driven through a porous structure at low Reynolds number, revealing heterogeneous concentration and velocity patterns.

Contribution

It provides detailed experimental insights into particle migration and flow behavior in porous media, highlighting the effects of particle concentration and porous geometry on flow heterogeneity.

Findings

Particles concentrate in free channels at higher volume fractions.

Velocity profiles become blunted with increasing particle concentration.

High concentration pathways form between rods in the porous medium.

Abstract

Laboratory experiments were conducted to study particle migration and flow properties of non- Brownian, non-colloidal suspensions ranging from 10% to 40% particle volume fraction in a pressure-driven flow over and through a porous structure at low Reynolds number. Particle concentration maps, velocity maps and corresponding profiles were acquired using a magnetic resonance imaging (MRI) technique. The model porous medium consists of square arrays of circular rods oriented across the flow in a rectangular microchannel. It was observed that the square arrays of the circular rods modify the velocity profiles and result in heterogeneous concentration fields for various suspensions. As the bulk particle volume fraction of the suspension increases, particles tend to concentrate in the free channel relative to the porous medium while the centerline velocity profile along the lateral direction becomes increasingly blunted. Within the porous structure, concentrated suspensions exhibit smaller periodic axial velocity variations due to the geometry compared to semi-dilute suspensions (bulk volume fraction ranges from 10% to 20%) and show periodic concentration variations, where average particle concentration is slightly greater between the rods than on top of the rods. For concentrated systems, high particle concentration pathways aligned with the flow direction are observed in regions that correspond to gaps between rods within the porous medium.